Five RNA extraction methods were compared for
the detection of citrus exocortis viroid (CEVd) by sequential
gel electrophoresis, using citron Etrog (Citrus medica) plants
inoculated with CEVd infected buds showing foliar epinasty.
The nucleic acid extraction methods evaluated, were those described by Pfannenstiel et al. (1980), Chomczynski and
Sacchi (1987), Pallás et al. (1987), Yang et al. (1992) and Lee
(1995). Following every extraction method, the RNA was
purified by column chromatography with CF-11 celullose. On
the basis of four replications, Lees method showed higher
values than the other methods, of total RNA per gram of
tissue (130 mg g-1); whereas, the method of Chomczynski
and Sacchi showed the lowest yields (53 mg g-1). Regarding
RNA quality, the method of Yang et al. Yielded an absorbance
relation 260/280 equal to 1.8, which is the minimum value
recommended; however, these extracts were contaminated
with DNA residues. All five extraction methods were
appropriate for the visualization of CEVd in electrophoresis
polyacrylamide gels. Likewise, CEVd extracted by any of the
evaluated methods, showed slight differences when
evaluated with a commercial hybridization kit of potato
spindle tuber viroid

Five RNA extraction methods were compared for
the detection of citrus exocortis viroid (CEVd) by sequential
gel electrophoresis, using citron Etrog (Citrus medica) plants
inoculated with CEVd infected buds showing foliar epinasty.
The nucleic acid extraction methods evaluated, were those described by Pfannenstiel et al. (1980), Chomczynski and
Sacchi (1987), Pallás et al. (1987), Yang et al. (1992) and Lee
(1995). Following every extraction method, the RNA was
purified by column chromatography with CF-11 celullose. On
the basis of four replications, Lees method showed higher
values than the other methods, of total RNA per gram of
tissue (130 mg g-1); whereas, the method of Chomczynski
and Sacchi showed the lowest yields (53 mg g-1). Regarding
RNA quality, the method of Yang et al. Yielded an absorbance
relation 260/280 equal to 1.8, which is the minimum value
recommended; however, these extracts were contaminated
with DNA residues. All five extraction methods were
appropriate for the visualization of CEVd in electrophoresis
polyacrylamide gels. Likewise, CEVd extracted by any of the
evaluated methods, showed slight differences when
evaluated with a commercial hybridization kit of potato
spindle tuber viroid